What to do?

Last spring my incredibly nice neighbor held a bible study in her apartment. I arrived home as they were leaving one night and one of our other neighbors invited me to join them. I have no desire to join a bible study and luckily I had class the night they met so I had a good reason and didn't have to come up with an excuse or explain my real reasons for not wanting to go.

And then yesterday she was clearly listening for me to come home and caught me on the stairs and told me about another bible study, this time one that is taking place at her church. She rather hurriedly told me a little about the group and then explained that she wasn't going to be able to go to all of the meetings and was hoping I could give a ride to two of the other women in our building. Again, I was totally thrown by the invite. I really don't want to alienate her, she is an awesome neighbor and it's clear religion is important to her. But being a non-Mormon from Utah I am very leery of conversion attempts. I realize it's totally possible she would accept and respect my lack of interest but that hasn't been my experience in the past. I don't want to have to explain to someone I actually know and like (as opposed to missionaries I don't know and only have to be polite to) that I have no interest in joining their church. As I was trying to figure out how to respond I realized that I have a class the night of this bible study too and had an easy and truthful excuse again. But what about next time? How do other people handle these situations?

Ironically the class I have at that time is on religion.